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A three-dimensional numerical simulation of oil shale in situ conversion processing by applying the downhole burner heating technology was conducted. The evolution of the fluid vector and temperature field and the characteristic of kerogen decomposition and oil and gas production were analyzed. The effects of different burning temperatures and gas injection velocities on the thermal evolution processing of oil shale in situ conversion were investigated. The stress-strain and deformation of the oil shale stratum during in situ processing were studied. The results show that kerogen decomposition is a thermo-kinetically controlled mechanism. Both the gas injection velocity and burning temperature can enhance the kerogen decomposition and oil production, especially for the latter one. In addition, the stratum-deformation of oil shale should be considered for oil shale in situ conversion processing, especially for the long-term operational lifetime., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The characterization of the concentration, chemical speciation and source of heavy metals in soils is an imperative for pollution monitoring and the potential risk assessment of the metals to animal and human health. A total of 154 surface horizons and 53 underlying horizons of grassland soil were collected from the Baicheng-Songyuan area in Jilin Province, Northeast China, in which the concentrations and chemical fractionations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were investigated. The mean concentrations of heavy metals in grassland topsoil were 7.2, 0.072, 35, 16.7, 0.014, 15.2, 18.3 and 35 mg kg(-)(1) for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn, respectively, and those averaged contents were lower than their China Environmental Quality Standard values for the Soils, implying that heavy metal concentrations in the studied soils were of the safety levels. The mobility sequence of the heavy metals based on the sum of the soluble, exchangeable, carbonate-bound and humic acid-bound fractions among the seven fractions decreased in the order of Cd 50.4%)>Hg (39.8%)>Cu (26.5%)>As (19.9%)>Zn (19.1%)>Ni (15.9%)>Pb (14.1%)>Cr (4.3%), suggesting Cd and Hg may pose more potential risk of soil contamination than other metals. Multivariate statistical analysis suggested that As, Cr, Cu, Ni, Pb, Zn, Cd and Hg had the similar lithogenic sources, however, Cd and Hg were more relevant to organic matter than other heavy metals, which was confirmed by the chemical speciation analysis of the metals. The study provides a base for local authority in the studied area to monitor the long term accession of heavy metals into grassland soil., (Copyright © 2015 Elsevier Ltd. All rights reserved.)